Water clarity in Lake Tahoe reached a record low annual average in 2017 due to a historic drought, record-breaking precipitation and warmer-than-usual lake temperatures, according to a new study.

The average annual clarity level for 2017 clocked in at 59.7 feet — a roughly 9.5-foot decrease from 2016 — and surpassed the previous recorded low of 64.1 feet in 1997, according to a report released by the Tahoe Environmental Research Center at UC Davis.

“The combination of arguably the most extreme drought period ending with the most extreme precipitation year produced the low clarity values seen,” said Geoffrey Schladow, the research center director. “But this does not reflect the long-term trend, and measurements for 2018 have already shown a large improvement ... more in line with the long-term trend.”

Clarity levels were “better” in mid-March 2017 but worsened in the fall and winter, when California recorded its second-wettest “water year” from October 2016 to September 2017, according to the report.

The Tahoe Basin recorded roughly 300 percent of its normal precipitation, which was bolstered by an early winter storm in November 2017.

“Lake Tahoe’s low clarity was primarily the result of two extreme climatic and hydrologic events — a perfect storm, so to speak,” Schladow said.

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California was nearing the end of its worst drought in roughly 1,200 years in 2017 and recorded heavy rains. This flushed sediment that accumulated in stream beds for five years during the drought, according to the report.

Summer temperatures last year were also the warmest on record at Lake Tahoe — nearly 3 degrees higher since 2014.

Those rising temperatures coupled with unusually low wind speeds in July and August caused warm water temperatures to last through September, which is later than normal for Lake Tahoe.

The water clarity report suggests that warming lake temperatures help in holding sediment particles to the surface of the water for a longer period of time, causing a drop in clarity.

Joanne S. Marchetta, executive director of the Tahoe Regional Planning Agency, said the research has helped scientists predict how a changing climate could affect the lake’s clarity.

“In response, we've been accelerating our investments in projects to bolster resiliency to emerging threats like extreme weather,” Marchetta said. “It’s important to continue to make those smart investments for the long-term health of the lake and its environment.”

Researchers with the Tahoe Environmental Research Center have been using water sensors and NASA buoys and manually collecting samples to help better understand under-examined areas of the lake during different weather conditions.